Photographic silver halide emulsion with silver halide grains having one twinning plane

ABSTRACT

This invention provides a photographic silver halide emulsion containing more than 30 percent by weight, based on the total silver halide crystals, of silver halide crystals which have only one twinning plane in a crystal and of which boundary planes with a dispersing medium comprise a (100) plane, a (111) plane or mixed planes thereof. The silver halide emulsion of this invention is monodispersible and provides a high optical sensitization rate and less occurrence of fog. Moreover, the emulsion has a high contrast characteristic and a high development rate. The emulsion of this invention has a further feature of reducing reciprocity law failure.

United States Patent 1 1 in] 3,885,970

Miyahara 1 1 May 27, 1975 PHOTOGRAPHIC SILVER HALIDE 3,817,756 6/1974 Claes et a1. 96/94 R EMULSION WITH SILVER HALIDE GRAINS HAVING ONE TWINNING PLANE [75] Inventor: Junji Miyahara, Kanagawa, Japan [73] Assignee: Fuji Photo Film Co., Ltd.,

Kanagawa, Japan [22] Filed: May 13, 1974 [21] Appl. No: 469,136

[30] Foreign Application Priority Data May 11, 1973 Japan 48-52390 [52] US. Cl 96/94 R; 96/95; 96/100; 96/109; 96/113; 96/114; 96/114.5; 96/114.7; 96/114.8; 96/114.9 [51] Int. Cl. G03c 1/02; G03c 1/06; (303C 1/48; 6030 l/40; G030 l/72; G030 1/38; G03c 1/34 [58] Field of Search 96/94 R; 423/491 [56] References Cited UNITED STATES PATENTS 3,655,394 4/1972 lllingsworth 96/94 R Primary ExaminerN0rman G. Torchin Assistant E.raminerRichard L. Schilling Attorney, Agent, or FirmSughrue. Rothwell, Mion, Zinn and Macpeak [57] ABSTRACT This invention provides a photographic silver halide emulsion containing more than 30 percent by weight, based on the total silver halide crystals, of silver halide crystals which have only one twinning plane in a crystal and of which boundary planes with a dispersing medium comprise a (100) plane, a (111) plane or mixed planes thereof. The silver halide emulsion of this invention is monodispersible and provides a high optical sensitization rate and less occurrence of fog, Moreover, the emulsion has a high contrast characteristic and a high development rate. The emulsion of this invention has a further feature of reducing reciprocity law failure.

7 Claims, 6 Drawing Figures PI-IOTOGRAPHIC SILVER I-IALIDE EMULSION WITH SILVER HALIDE GRAINS HAVING ONE TWINNING PLANE BACKGROUND OF THE INVENTION l. Field of the Invention The present invention relates to a photographic silver halide emulsion and, particularly, to a photographic silver halide emulsion containing silver halide of a specific crystal structure and having excellent photographic properties.

2. Description of the Prior Art Crystals of silver halides in photographic emulsions are generally classified into several forms and most of the crystal grains are present as plate crystals, needle crystals, regular octahedral crystals, regular hexahedral crystals, tetradecahedral crystals, and sperical crystals having dissolved edges and thus indistinct boundary planes. It is also known that special irregular crystals other than the above forms are present in a very small amount in photographic emulsions. It is well recognized in the photographic field that these special irregular crystal grains should be removed to the extent possible from the photographic emulsion in order to narrow the distribution of the grain sizes of the silver halide emulsion, or to reduce the sensitivity scatter. On the other hand, a method of forming emulsion grains which can freely control the content of these special irregular crystals is not at present known and, therefore, the photographic properties of a photographic emulsion having these special irregular crystals have not yet been demonstrated.

SUMMARY OF THE INVENTION An object of this invention is to provide a photo graphic silver halide emulsion having a novel composition.

Another object of this invention is to provide a photographic silver halide emulsion with a high optical sensitization rate.

A further object ofthis invention is to provide a photographic silver halide emulsion with a narrow distribution of grain sizes.

A still further object of this invention is to provide a direct positive photographic emulsion with a high sensitivity which is substantially uniformly fogged.

Research has been conducted to attain the above objects and it has suprisingly been found that the aforesaid special irregular crystals of silver halide provide very specific photographic properties.

This invention provides a photographic silver halide emulsion containing more than 30 percent by weight of silver halide crystals which have only one twinning plane in a crystal and of which boundary planes with a dispersing medium comprise a (100) plane, a (111) plane or mixed planes thereof, based on the totai weight of the silver halide crystals.

BRIEF EXPLANATION OF THE DRAWINGS FIGS. 1 to 6 are schematic illustrations of irregular grains contained in a silver halide emulsion of this invention.

DETAILED DESCRIPTION OF THE INVENTION The photographic silver halide emulsion of this invention is similar to conventional emulsions in that SII- ver halide grains are suspended in a dispersing medium,

but differs in that more than 30 percent by weight of crystal grains of the total silver halide grains have only one twinning plane and their boundary planes with the dispersing medium include the (I00) plane, the (111) plane or mixed planes thereof. In the photographic field, plate crystals or needle crystals having multiple twinning planes, regular hexahedral crystals which have no twinning planes and of which the boundary planes with a dispersing medium are the (I00) plane, regular octahedral crystals of which the boundary planes are the (111) plane and tetradecahedral crystals having both the (I00) plane and the (III) plane are well known, and they have been used as photographic silver halide light-sensitive materials. These crystals are described, for example, in C.E.I(. Mees & T. H. James. The Theory of the Photographic Process by Chapter 2, Third Edition, MacMillan Co., (I966). Therefore, these crystal planes are well known and understood by those skilled in the art.

Irregular grains contained in the silver halide emulsion of this invention are found to have the structures as shown in FIGS. I to 6 by electron microscopic analy sis. Thus, these grains apparently differ from the afore' said silver halide crystals used for conventional photographic light-sensitive materials and, their photographic properties are also clearly different.

An example of one of the photographic properties of a photographic emulsion containing grains of such special forms is monodispersibility. Photographic emulsions having the usual crystal structures described above require various techniques for producing monodispersed emulsions because of the unevenness in grain size, while the silver halide emulsion of this invention inherently is monodispersibile and thus conventional procedures for attaining monodispersibility are not necessary. While not desiring to be bound, it is believed, this monodispersibility is apparently due to the irregular grains of this invention. Therefore, greater monodispersibility is obtained as the number of irregular grains in the emulsion increases. In this respect, the content of such irregular grains is desirably more than 30 percent by weight, preferably more than 50 percent by weight, to total weight of the silver halide crystals. Other silver halide crystals contained in the photographic emulsion of this invention can be those forms which are well-known in the prior art.

The special irregular grains contained in the silver halide emulsion of this invention have characteristics of providing a very excellent monodispersibility, a higher contrast as compared with usual photographic emulsions, a reduced reciprocity law failure, and an improved development rate. The irregular grains have the further characteristic of providing a higher optical sensitization rate and less occurrence of fog than those emulsions containing conventional crystal grains. Moreover, the irregular grains can increase the direct reversal sensitivity of a direct reversal emulsion which is uniformly fogged or a direct reversal emulsion of the internal latent image type which provides fog nuclei on development as compared with conventional crystal grains.

The silver halides which can be used in this invention include silver halides which are well-known in the art such as silver chloride, silver bromide, silver bromochloride, silver bromoiodide or silver bromoiodochloride.

Silver halide emulsions comprise a silver halide suspended in a hydrophilic binder. Suitable hydrophilic binders are, for example, gelatin. colloidal albumin casein, cellulose derivatives such as carboxymethyl cellu lose or hydroxyethyl cellulose. polysaccharides such as agar, sodium alginate or starch derivatives, synthetic hydrophilic colloids such as polyvinyl alcohol, poly-N- vinyl-pyrrolidone, polyacrylic acid copolymers, po1y acrylamide or the derivatives thereof and the like. If desired, compatible mixtures of such colloids can be used. Of the colloids, gelatin is most generally used and can be replaced partially or completely with synthetic high molecular weight substances. Moreover, gelatin can be replaced with the so-called gelatin derivatives in which the amino, imino, hydroxy or carboxyl functional groups in gelatin molecule are reacted with a compound having one group capable of reacting with such functional groups, or gelatin graft polymers in which gelatin is combined with the molecular chain of another high molecular weight substance.

Examples of compounds which can used for producing the above gelatin derivatives are isocyanates, acid chlorides and acid anhydrides as described in U.S. Pat. No. 2,614,928, acid anhydrides as described in U.S. Pat. No. 3,118,766, bromoacetic acids as described in Japanese Pat. Publication No. 5514/64, phenylglycidyl ethers as described in Japanese Pat. Publication No. 26845/67, vinyl sulfone compounds as described in US. Pat. No. 3,132,945, N-allylvinylsulfonamides as described in British Pat. No. 861,414, maleinimide compounds as described in U.S. Pat. No. 3,186,846, acrylonitriles as described in U.S. Pat. No. 2,594,293, polyalkylene oxides as described in U.S. Pat. No. 3,312,553, epoxy compounds as described in Japanese Pat. Publication No. 26,845/67, esters of acids as described in U.S. Pat. No. 2,763,639, alkane sultones as described in British Pat. No. 1,033,189, etc.

Suitable high molecular weight substances which can be grafted to gelatin, are disclosed, for example, in U.S. Pat. Nos. 2,763,625, 2,831,767 and 2,956,884, or Polymer Letters, 5, 595 (1967), Photo. Sci. Eng, 9, 148 11965), J. Polymer Sci, A-l, 9, 3199 1971 etc. Poly mers or copolymers of those materials generally designated as vinyl monomers, such as acrylic acid and methacrylic acid, or the derivatives thereof, for example, the ester, amide or nitrile derivatives, or ethylene can be widely used. Particularly preferred are hydrophilic vinyl polymers having some degree of compatibility with gelatin, for example, polymers or copolymers of acrylic acid, acrylamide, methacrylamide, hydroxyalkylacrylate, hydroxyalkyl methacrylate, etc.

The silver halide emulsions are prepared by mixing a solution of water-soluble silver salt (for example, silver nitrate) with a solution of a water-soluble halide in the presence of a solution of water soluble high molecular weight substance. These silver halide grains can be prepared using conventional procedures. The so-called single or double jet method, the controlled double jet method, etc. are, of course, useful.

Care should be taken in the production of photographic silver halide emulsions of this invention to increase the probability that stacking faults will be generated in the step of forming the nuclei ofthe silver halide crystals on reacting the silver ion with the halide ion.

It has been found in the course of studying the formation of crystal grains that special irregular crystals of this invention can be formed in a much larger ratio than in conventional emulsion, if the following conditions are satisfied:

1. ln forming precipitates of silver halide crystals by simultaneously adding an aqueous solution of silver nitrate and an aqueous solution of a halide, that is, in the formation of grains by the twin jet method well-known in the photographic field, the silver ion concentration on forming precipitates must be kept in the range of from the equivalence point in the reaction of Ag X AgX(in which X is halide ion) to the point of ApAg l. (in

2. The concentrations of an aqueous solution of silver nitrate and an aqueous solution of the halide to be added must be kept in the range of from a 2 normal concentration to the saturation point at normal temperatures.

3. At least in the initial stage of forming the silver halide precipitates, no solvent for silver halide is present.

4. More significantly, and aqueous solution of silver nitrate and an aqueous solution of the halide must be added and rapidly mixed in the formation of precipitates near the equivalence point so that the change of silver ion concentration (AEAg) in the reaction zone is less than 2 mV, preferably less than 1 mV.

In addition for forming the special irregular silver halide grains of this invention, a substance which is adsorbed on a specified plate of the crystal in nuclei forming stage to inhibit the growth of such plate can be in croporated, or the irregular grains contained as impurities can be separated using a centrifugal separation in preparing conventional photographic silver halide emulsions, taking advantage of the fact that the average size of the irregular grains is larger than the average size of cubic grains.

In preparing the silver halide emulsion, usual methods such as physical ripening, desalting or chemical ripening (for example, gold sensitization, sulfur sensitiza tion) can be employed. These methods are described in The Theory of the Photographic Process, described above, Grafikides, Photographic Chemistry, and the like.

The silver halide emulsions of this invention can contain optical sensitizers such as cyanine dyes, merocya nine dyes or hemicyanine dyes, stabilizing agents such as 4-hydroxy-6-methyl-l ,3,3a,7-tetrazaindene, sensitizers such as the compounds as described in U.S. Pat. No. 3,619,198, antifogging agents such as benzotriazole, 5-nitrobenzimidazole or a polyalkylene oxide, hardening agents such as formaldehyde, glyoxal, mucochloric acid or 2-hydroxy-4,6-dichloros-triazine, coating aids such as saponin, sodium lauryl sulfate, dodecylphenol polyethylene oxide ether or hexadecyltrimethyl ammonium bromide, development accelerators such as the compounds as described in U.S. Pat. No. 3,345,175,

color couplers as described in U.S. Pat. Nos. 3,311,476; 3,006,759; 3,277,155; 3,214,437; 3,253,924; 2,600,788; 2,801,171; 3,252,924; 2,698,794; 2,474,293; 3,458,315; 3,476,560; 3,034,892; 3,386,301; 2,434,272; 3,476,564; 3,148,062; 3,227,554; 3,701,783; 3,617,291; and

3,622,328, British Pat. Nos. 1,140,898 and 904,852, Japanese Pat. Publication Nos. 6031/65; 2016.69 and 28836/70, Japanese Pat. application Nos. 45971/73 and 33238/73 and German OLS 2,163,811, agents for improving dimensional stability such as the compounds as described in U.S. pat. No. 3,516,830 or the additives as described in U.S. Pat. Nos. 3,501,305; 3,501,306;

3,501,307; 3,501,310; 3,531,288; 3,531,290; 3,367,778; 3,477,852 and 3,512,985. These additives can be added during the preparation of the silver halide emulsions or just before the coating thereof.

The silver halide emulsions thus obtained can be applied in a single layer or multi layers on one side or both sides of conventional supports such as glass, baryta paper, resin-coated paper, for example, a polyethylene laminated paper, cellulose acetate film or polyethylene terephthalate film using dip coating, air-knife coating, bead coating, extrusion doctor coating, curtain coating or simultaneous coating on both sides. In addition to the silver halide emulsion layer, a backing layer, intermediate layers, an antihalation layer, a surface layer (for example, protective layer), etc. can be applied.

The silver halide emulsion of this invention is monodispersible and provides a high optical sensitization rate and less fog occurrence. Moreover, the silver halide emulsion of this invention has a high contrast and a high development rate. The emulsion of this invention further has the feature of reducing the reciprocity law failure. By virtue of these specific photographic properties, the emulsion of this invention can be used in various applications, for example, in monochromic photographic light-sensitive materials such as microfilm photographic materials, lith type photographic ma terials, direct reversal photographic materials of the surface latent image type or the internal latent image type, medical or industrial X-ray photographic materials, negative photographic materials or photographic papers, and color photographic light-sensitive materials such as color negative photographic materials, color positive photographic materials, color papers or color reversal photographic materials.

The silver halide emulsion of this invention is developed with an aqueous alkaline solution containing a developing agent. Suitable developing agents are those generally known in the art, for example, dihydroxybenzenes such as hydroquinone, chlorohydroquinone, bromohydroquinone, isopropylhydroquinone, toluhydroquinone, methylhydroquinone, 2,3- dichlorohydroquinone, or 2,5-dimethylhydroquinone; 3-pyrazolidones such as l-phenyl-3-pyrazolidone, lphenyl-4-methyl-3-pyrazolidone, lphenyl4,4-dimethy1-3pyrazolidone, l-phenyl-4-ethyl-3-pyrazolidone or l-phenyl-5-methyl-3-pyrazolidone; aminophenols such as o-aminophenol, p-aminophenol, N-methyl-oaminophenyl, N-methyl-p-aminophenol or 2,4- diaminophenol; pyrogallol', ascorbic acid; l-aryl-3- aminopyrazolines such as l-(p-hydroxyphenyl)-3- aminopyrazoline, l-(p-methylaminophenyl)-3- pyrazoline, 1-(p-aminophenyl)-3-aminopyrazoline or 1-(p-amino-m-methylphenyl)-3-aminopyrazoline; para-phenylenediamines such as 4-amino-3-ethoxy- N,N-diethylaniline, 4-amino-3,5-dimethyl-N,N-diethylaniline, 4-amino-3-methyl-N-ethyl-N-(B-hydroxyethyl- )aniline, 4-amino-3-methyl-N,N-diethylaniline, 4- amino-3-methyl-N-ethyl-N-( B-methylsulfonamidoethyl)aniline, 4-amino-3-(B-methylsulfonamidoethyl)- N,N-diethylaniline, 4-amino-N-ethyl-N-(B-hydroxyethyl)aniline, 4-amino-N,N-diethylaniline or 4-amino- N-ethyl-N-a-sulfobutylaniline; or mixtures thereof.

The developers can contain, if desired, antioxidants such as sulfites or bisulfites, buffers such as carbonates, boric acid, borates or alkanolamines, alkali agents such as hydroxides or carbonates, dissolution promoters such as polyethylene glycols or esters thereof, pH adjusting agents such as organic acids. for example, acetic acid, sensitizers such as quaternary ammonium salts, development accelerators, surface active agents, etc.

Dialdehyde compounds also can be added to the developers. Suitable dialdehyde compounds include the bisulfite adducts thereof, and they are specifically described in U.S. Reissue Pat. No. 26,601, U.S. Pat. No, 3,545,971, etc. Examples of suitable dialdehydes are glutaraldehyde, a-methylglutaraldehyde, B-methylglutaraldehyde, maleindialdehyde, succindiuldehyde, methoxysuccindialdehyde, methylsuccindialdehyde, a-methoxy-B-ethoxyglutaraldehyde, a-nbutoxyglutaraldehyde, a-ethyl-B- ethoxyglutaraldehyde, a,a-dimethoxysuccindialdehyde B-isopropylsuccindialdehyde, 0:,a-diethylsuccindialdehyde, butylrnaleindialdehyde or the bisulfite adducts thereof. The dialdehyde compounds are used in such amounts in which the sensitivity of a photographic layer to be processed is not reduced and in which the drying time is not extended remarkably. Generally, from 1 to 50 g, preferably 3 to 20 g, of the dialdehyde per liter of the developer is suitable. In some cases, the developers can contain a sulfite ion buffer, for example, a sodium hydrogensulfite adduct of an aldehyde such as the hydrogensulfite hydrogensulfite adduct of formaldehyde, an alkali metal hydrogensulftie adduct of a ketone, such as the sodium hydrogensulfite adduct of acetone, a carbonylbisulfite-amine condensate such as sodium-bis(2-hydroxyethyl)aminomethanesulfonate, and the like in amounts of 13 to g per liter of a developer.

The developers can further contain agents for dispersing colloidal silver leached out, for example, mercapto compounds; antifogging agents, for example, halides such as potassium bromide or sodium bromide, benzotriazole, benzothiazole, tetrazole, thiazole, etc.; chelating agents, for example, ethylenediamine tetraacetate, or the alkali metal salts thereof, polyphosphate, nitriloacetate, etc.

The pH of the developers thus prepared depends on the intended purposes, and in most cases, a pH greater than 7 is used.

The photographic silver halide emulsion which has been developed is fixed with a fixing bath in accordance with conventional procedures. Examples of suitable fixing agents are thiosulfates such as sodium thiosulfate, thiocyanates such as potassium thiocyanate, sulfur-containing organic dibasic acids such as bisthioglycollic acid, organic diols such as 3-thia-l ,5- pentadiol, or imidazolidinthione.

The fixing bath can contain, if desired, antioxidants such as sulfites or bisulfites, pH buffers such as boric acid or borates, pH adjusting agents such as acetic acid, and chelating agents as described above.

In addition to the above steps, the processing can include, if desired, a pre-hardening bath, a neutralizing bath, a stop bath, a bleach bath (or bleach-fix bath including the above fixing), a stabilizing bath, washing, etc. Moreover, the processing can be effected using an apparatus as described in U.S. Pat. No. 3,025,779 according to the procedure as described in U.S. Pat. No. 3,545,971.

This invention will be further described in greater detail by reference to the following examples. Unless otherwise indicated, all parts, percentages, ratios and the like are by weight.

EXAMPLE 1 A 4 molar aqueous solution of silver nitrate and a 4 molar aqueous solution of potassium bromide were added simultaneously to a solution of 5 g ofgelatin dissolved in 500 ml of distilled water at 60C, and the addition was continued with stirring so that pAg was +l40 mV represented in millivolt units and the potential change with respect to time of an electrode for measuring the pAg in the reaction zone was within :1 mV. The formation of precipitates was continued for 60 minutes and finally an aqueous solution of potassium iodide was further added so that the l ion content was 2 mol percent with respect to the amount of Ag ion, Thus, a silver bromoiodide emulsion containing about 70 percent by weight of irregular crystal grains with a grain size of about 0.3 p. and containing about 30 percent by weight of usual cubic crystal grains was obtained (Emulsion A]. This emulsion was washed to remove water-soluble salts produced as by-products, and after adding 20 g of gelatin, the emulsion was again dis solved. Separately, a silver bromoiodide emulsion con taining more than 90 percent by weight of usual cubic crystal grains (Emulsion B) was prepared by using the same pAg potential as for Emulsion A but using a potential change with respect to time of more than 50 mV. To each of Emulsion A and B, 2 mg of phenylhydrazine hydrochloride was added per 20 g of silver bromoiodide, and the emulsions were each heated at 50C for minutes. Furthermore, 1 mg of sodium chloroaurate was added to each emulsion, followed by heating each emulsion for minutes. To each of the fogged emulsions thus obtained, 50 mg/mol of pinacryptol yellow as an electron acceptor dye was added, and each of the emulsions was then applied to a cellulose triacetate film. After exposure and development, Emulsion A showed direct reversal characteristics of a higher reversal sensitivity and a wider exposure latitude (that is, a more soft gradation) as compared with Emulsion B, although the maximum photographic density of Emulsion A and emulsion B was the same.

The formation of precipitates of silver chloride crystals was effected by dissolving 10 g of gelatin in 1,000 ml of distilled water and then adding, to this solution, a 2 molar aqueous solution of silver nitrate, and simultaneously an aqueous solution of sodium chloride in an amount equal to that of the aqueous solution of silver nitrate so that the chloride ion was 5 mol percent in ex cess of the silver ion.

In this example, an emulsion prepared under the same condition of addition and agitation as described for Emulsion A in example 1 was a silver chloride emulsion containing about 80 percent by weight ofirregular crystal grains of a grain size of about 0.4 p and about 20 percent by weight of usual cubic grains (Emulsion C). Moreover, an emulsion of the same type but containing more than 90 percent by weight of cubic grains was prepared by conventional procedures (Emulsion D). Emulsion C and D were sulfur-sensitized by usual procedures. Furthermore, each of the emulsions were divided into two parts, and one group was applied as such to a polyethylene terephthalate film, and the second group was spectrally sensitized by adding a merocyanine dye and then applied to a polyethylene terephthalate film. After exposure and development. Emulsion C showed higher sensitivity and a harder gradation than the sensitivity and gradation of Emulsion D, even before spectral sensitization. After spectral sensitization, the sensitivity of Emulsion C was remarkably increased due to the dye as compared with the sensitivity of Emulsion D.

Table 2 Photographic Emulsion An emulsion containing percent by weight of irregular crystals was prepared under the same potential conditions as described for Emulsion A in Example 1 and by adding potassium iodide just before the formation of precipitates. When this emulsion was subjected to sulfur sensitization and gold sensitization, photographic characteristics of a higher sensitivity after adding a sensitizing dye and higher contrast were obtained, as compared with an emulsion containing more than percent by weight of cubic grains and subjected to similar sensitization.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

What is claimed is:

1. A photographic silver halide emulsion comprising a dispersing medium containing silver halide crystals of which a proportion of more than 30 percent by weight of the silver halide crystals have only one twinning plane in each crystal and of which the boundary planes with the dispersing medium comprise a plane, a (111) plane or mixed (100) and (111) planes to the total silver halide crystals.

2. The photographic silver halide emulsion of claim 1, wherein said proportion is more than 50 percent by weight of the silver halide crystals.

3. The photographic silver halide emulsion of claim 1, wherein said silver halide crystals are crystals of silver chloride, silver bromide, silver bromochloride, silver bromoiodide or silver bromoiodochloride.

4. The photographic silver halide emulsion of claim 1, wherein said dispersing medium is a hydrophilic binder.

1, wherein said emulsion includes at least one of an optical sensitizer, a stabilizing agent, an antifogging agent, a coating aid, a development accelerator, a color coupler and a dimensional stability improving agent.

7. A photographic light-sensitive element comprising a support having thereon a layer of the photographic silver halide emulsion of claim 1. 

1. A PHOTOGRAPHIC SILVER HALIDE EMULSION COMPRISING A DISPERSING MEDIUM CONTAINING SILVER HALIDE CRYSTALS OF WHICH A PROPORTION OF MORE THAN 30 PERCENT BY WEIGHT OF THE SILVER HALIDE CRYSTALS HAVE ONLY ONE TWINNING PLANE IN EACH CRYSTAL AND OF WHICH THE BONDARY PLANES WITH THE DISPERSING MEDIUM COMPRISE A (100) PLANE, A (111) PLANE OR MIXED (100) AND (111) PLANES TO THE TOTAL SILVER HALIDE CRYSTALS.
 2. The photographic silver halide emulsion of claim 1, wherein said proportion is more than 50 percent by weight of the silver halide crystals.
 3. The photographic silver halide emulsion of claim 1, wherein said silver halide crystals are crystals of silver chloride, silver bromide, silver bromochloride, silver bromoiodide or silver bromoiodochloride.
 4. The photographic silver halide emulsion of claim 1, wherein said dispersing medium is a hydrophilic binder.
 5. The photographic silver halide emulsion of claim 4, wherein said hydrophilic binder is gelatin, a gelatin derivative, a graft gelatin, colloidal albumin, casein, carboxymethyl cellulose, hydroxyethyl cellulose, agar, sodium alginate, a starch derivative, polyvinyl alcohol, poly-N-vinyl-pyrrolidone, a polyacrylic acid copolymer, a polyacrylamide, a polyacrylamide derivative, or a mixture thereof.
 6. The photographic silver halide emulsion of claim 1, wherein said emulsion includes at least one of an optical sensitizer, a stabilizing agent, an antifogging agent, a coating aid, a development accelerator, a color coupler and a dimensional stability improving agent.
 7. A photographic light-sensitive element comprising a support having thereon a layer of the photographic silver halide emulsion of claim
 1. 